The present invention generally refers to jet-injection syringes and, more particularly, to disposable unit-dose jet injection syringes.
Jet injection instruments were being developed as early as the 1940""s. The developments included a hypospray injector, which regulates the dosage, with an attached body containing the drug. F. H. J. Figge and D. J. Barnett, Anatomic Evaluation of a Jet Injection Instrument Designed to Minimize Pain and Inconvenience of Parental Therapy, AMER. PRACTITIONER 197-206 (December 1948). Several jet-injection systems with reusable syringes are known. The reusable systems, however, have proven to offer little if any protection for cross contamination between subjects. In light of research that many diseases can be passed between subjects via jet injections, e.g. HIV, hepatitis, etc., these reusable systems become an unacceptable method for mass injection and/or vaccination.
There have been attempts to overcome the problem of cross contamination by offering jet-injection systems with disposable plastic jet-injection syringes. While these disposable plastic jet-injection syringes have somewhat overcome the potential for cross contamination, they introduce several other problems such as incompatibility with long term storage and increased manufacturing costs.
These plastic jet-injection syringes are made of a limited family of polymers, mostly polycarbonate, that can withstand high pressures associated with jet injection (in the range of 2000 to 10,000 psi). These polymers, however, have either a limited or no long-term shelf life because of the potential leaching of chemical extractables from the polymers into the liquid compound to be injected thereby causing contamination.
The plastic jet-injection syringes also require a relatively thick wall section to withstand the large pressure spike produced during jet injection. The microscopic orifice needed to obtain sufficient fluid velocity for skin penetration and subsequent deposition of the liquid requires that the liquid must travel a relatively long distance to pass through the thick wall. The ratio of orifice length to orifice diameter is typically over 10:1. This long distance in relationship creates a high manufacturing cost to form the orifice and creates several further technical difficulties. First, the high length-to-diameter ratio is difficult to produce with consistent orifice quality. Second, the high length-to-diameter ratio generates velocity loss, thereby requiring a greater initial force to achieve the required injection velocity which adds cost and greater bulk to the pressure generation system.
Injectable medications for human applications are traditionally supplied to the end user, not in the syringe that will be used to inject the medication into the patient, but in a secondary container, or multiple secondary containers for the case of lyophilized vaccines. Before the medication can be injected into the patient, it must be transferred into the syringe, which is filled to the appropriate level (trans-filled).
Another problem associated with existing systems is the lack of an efficient and safe method for transfilling an empty sterile unit dose syringe with liquid compound from a bulk source. There have been several attempts to address this problem with varying degrees of success. Most methods employ a needle or compound bottle puncturing spike temporarily attached to the jet injection syringe. Liquid is drawn from the bottle into the syringe through the needle or spike by a vacuum created when a piston is retracted in the syringe. There are a number of unit dose needle free injection or jet injection systems available on the market today (Bioject(copyright), J-tip(copyright), Injex(copyright), etc.). For all these devices, the accepted method of filling the injector cartridge emulates the same procedure that is used for filling a standard needle injector. This is a slow, some times messy (because of the nature of the distal end of the jet injector syringe), and potentially hazardous operation (in reference to the use of a needle and potential needle stick injury) for transfilling appears to be at cross-purposes with the primary goal of eliminating sharps from the administration of medications.
Accordingly, there is a need in the art for an improved disposable jet-injection syringe and method of making the same which allows long term shelf life without leaking chemicals and can be produced at a relatively low cost. Further, there is a need in the art for an improved disposable jet-injection syringe with a metal thin wall which reduces the piston length, reduces manufacturing costs, reduces inconsistent orifice quality, and reduces piston force while withstanding piston pressure. Additionally, there is a need in the art for an improved device and method for transfilling an empty sterile unit dose syringe which is efficient and safe without the need of needles that would present sharps hazards to medical personnel. Additionally, there is a need in the art for an improved device which can be transfilled from a bulk source. Further, there is a need of transfilling from a bulk source which can be transfilled from an end located away from the injection area. Additionally, there is a need in the art for a method of manufacturing an improved disposable jet injection syringe. Accordingly, there is a need in the art for a method of injecting medication with an improved disposable jet injection syringe.
Disclosed is a disposable unit-dose jet injection syringe having a cylindrically shaped body. The body has a rear open end and a forward closed end with a cavity disposed therebetween. The rear open end has an enlarged diameter forming a flange that retains the syringe to a driving system during the injection cycle. The closed end has a small area coined by a stamping process. A jet orifice is punched through the small area of the closed end. The thickness of the coined area may be substantially equal to the diameter of the orifice. A piston is movably positioned within the syringe body to form a cavity for holding a unit dose of liquid, powder, drug, or biological.
The present invention further relates to a method of manufacturing a unit-dose jet injection syringe comprising stamping a body. Next, the method forms a forward closed end and a rear open end on the body. Then, a jet orifice is stamped through the forward closed end. The method then provides injection molding a piston from a polymer material and removably attaching the piston inside the metal body. The present invention further provides a method of injecting medicine comprising connecting a disposable syringe having a cavity to a driving system. A piston is then activated through the cavity. The method next provides injecting the unit dose by the piston through a jet orifice into a subject. After the unit dose has been injected, the disposable syringe is disconnected.
The present invention further relates to an apparatus and method for transfilling a disposable unit-dose jet injection syringe.